1. Technical Field
The present inventions relate to transcoders and, more particularly, relate to management of transcoding with cache.
2. Description of the Related Art
Video signals have traditionally been broadcast from terrestrial transmission towers direct to the home, or broadcast from uplink centers to orbiting satellites for retransmission to the home, or the video may have been broadcast/distributed using public or privately-owned cable television networks. Today, as internet infrastructure continues to improve, more and more video is being uploaded, stored and maintained within the internet cloud, and more and more content is being distributed to media-capable viewing devices including set top boxes, television receivers, smart phones, notebooks, tablets and desktop computers. New viewing habits are also emerging. In addition to the more passive model of selecting broadcast content by channel surfing or scanning program guides, viewers are also using interactive searching tools and services to scan from libraries of individualized content and are interactively controlling the way this content is streamed to their personal media-playing device. For example, if the content is unicasted instead of broadcasted, then the user may be able to pause, change playback speed, or manage the streaming of content in various other ways without depending on local storage devices to implement the time-shifting functions.
As the variety of content origination sources increases, so has the diversity of compression formats, video quality, and data rate requirements for real-time streaming. At the same time, the capabilities of the various media playback devices have also become more variable and diverse. This raises the problem of compatibility mismatches.
Most media playback devices only support a small subset of the commonly used compression formats, which include H.264, VC1, MPEG4 ASP, MPEG2, MPEG1, H.263, Theora, and additional codecs associated with the FLASH container format. Similar compatibility mismatches occur between the audio codec formats and audio decoding capabilities of the client devices, and even more variability exists in the choice of container format used to merge the various video, audio and data components into a single stream. The problem is further complicated by the unpredictability of the underlying capacity of the network which can vary by transmission medium, region, and time of day. For example, a typical cellular network relied upon by mobile devices may be incapable of accommodating a high quality HD video stream even under the best of conditions. These problems are often dealt with by controlling the range of client devices that may be used to access a particular subset of content, in much the same way that cable companies have restricted their customers to use certain set top box models. A better alternative is to modify the video and audio content so that it becomes compatible with both the client device that is requesting the content, as well the network that is delivering it.
The problem of converting video and audio signals from one format to another, and/or from one data rate and quality level to a lower data rate and quality level, has been solved. Transcoders exist for this purpose. Unfortunately, transcoding to or from one of the more efficient video compression formats such as H.264 can be expensive, and usually requires dedicated hardware depending on the number of streams to be processed, real-time requirements, resolution, frame rate, and budget. As transcoding capacity is scaled to keep up with constantly increasing traffic demands, the efficiency, complexity, and cost of the transcoding solution becomes more critical. An efficient and scalable high-capacity transcoding solution is needed.